• The effect of melt viscosity on thermal efficiency for single screw extrusion of HDPE

      Vera-Sorroche, Javier; Kelly, Adrian L.; Brown, Elaine C.; Gough, Timothy D.; Abeykoon, Chamil; Coates, Philip D.; Deng, J.; Li, K.; Harkin-Jones, E.; Price, M. (2014-11-11)
      In this work, a highly instrumented single screw extruder has been used to study the effect of polymer rheology on the thermal efficiency of the extrusion process. Three different molecular weight grades of high density polyethylene (HDPE) were extruded at a range of conditions. Three geometries of extruder screws were used at several set temperatures and screw rotation speeds. The extruder was equipped with real-time quantification of energy consumption; thermal dynamics of the process were examined using thermocouple grid sensors at the entrance to the die. Results showed that polymer rheology had a significant effect on process energy consumption and thermal homogeneity of the melt. Highest specific energy consumption and poorest homogeneity was observed for the highest viscosity grade of HDPE. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. In particular, specific energy consumption was lower using a barrier flighted screw compared to single flighted screws at the same set conditions. These results highlight the complex nature of extrusion thermal dynamics and provide evidence that rheological properties of the polymer can significantly influence the thermal efficiency of the process. (C) 2014 The Authors. Published by Elsevier B.V. All rights reserved.
    • The effect of particle shape and size distribution on the acoustical properties of mixtures of hemp particles

      Glé, P.; Gourdon, E.; Arnaud, L.; Horoshenkov, Kirill V.; Khan, Amir (2013)
      Hemp concrete is an attractive alternative to traditional materials used in building construction. It has a very low environmental impact, and it is characterized by high thermal insulation. Hemp aggregate particles are parallelepiped in shape and can be organized in a plurality of ways to create a considerable proportion of open pores with a complex connectivity pattern, the acoustical properties of which have never been examined systematically. Therefore this paper is focused on the fundamental understanding of the relations between the particle shape and size distribution, pore size distribution, and the acoustical properties of the resultant porous material mixture. The sound absorption and the transmission loss of various hemp aggregates is characterized using laboratory experiments and three theoretical models. These models are used to relate the particle size distribution to the pore size distribution. It is shown that the shape of particles and particle size control the pore size distribution and tortuosity in shiv. These properties in turn relate directly to the observed acoustical behavior.
    • The effects of "greening" urban areas on the perceptions of tranquility

      Watts, Gregory R.; Pheasant, Robert J. (2015)
      A number of studies have been conducted at the Bradford Centre for Sustainable Environments at the University of Bradford which have examined the effects of natural features on ratings of tranquillity. These include quantifying the effects of the percentage of natural and contextual features and man-made noise on rated tranquillity. Recently the resulting prediction equation TRAPT (Tranquillity Rating Prediction Tool) has been used to examine a number of scenarios including city parks and square, country parks and moorland areas and to relate predictions to ratings made by visitors to these green spaces and reported levels of relaxation. The tool has also been used for predicting tranquillity in city squares of different sizes, to examine tranquillity behind natural (green) and manufactured noise barriers and to assess the benefits of “greening” streets in urban areas using avenues of trees, hedges and grass verges. The paper reviews these studies and gives examples of the extent to which introducing vegetation is predicted to provide benefits.
    • The experimental and numerical approach of two-phase flows by wall jets on rough beds in open channel flow

      Ghoma, Mohamed Ibrahem; Hussain, Khalid; Tait, Simon J. (2014)
      This paper presents the results of investigations carried out to study the effect of horizontal wall jets on a fixed rough bed in an open channel. The study used both numerical and experimental approaches. The numerical and experimental studies are compared for validation. The main objective of this study is to understand the effect of wall jets on a horizontal fixed rough bed in an open channel. The experimental study investigated the effect of wall jets on a fixed horizontal bed, with a known roughness in an open channel flume. A sid-looking Acoustic Doppler Velocimetry (ADV) was used to measure the velocity profile of the flow at different flow zones. The wave monitor was used to measure the free surface during the experiments. Computational fluid dynamics CFD simulations were conducted in a rectangular channel to compare with the laboratory tests using the volume of fluid VOF multiphase method and K- ࢿ model. The two phase (water and air) was used in this study. Computer simulations for the model were used to predict the fluid horizontal velocity (u) revealing the characteristics of the wall jet over different flow zones (developing, fully developed and recovering zones). The results showed that the velocity profiles distribution in the stream wise direction in the channel were reasonable. The reverse velocity was close to the wall jet and the maximum reverse velocity was observed near the water surface. Also the results showed that the depression was close to the wall jet. The agreement between the results obtained from the numerical and the experimental data were reasonable.
    • The Influence of Pad Abutment on the Generation of Brake Noise

      Fieldhouse, John D.; Bryant, David; Talbot, C.J. (2011)
      The paper overviews the modes of vibration of the principal component parts of a brake and their contribution to system instability during noise generation. It is shown that both in-plane and out-of-plane vibration is present and that both can be related to the vibration of the pad. It is further shown that the pad and its region often provide a solution or 'fix' towards noise prevention and it is this area that forms the focus of this investigation. The collective evidence, proposals and associated theory are applied to real brake case studies when it is demonstrated that disc/pad interface 'spragging' may be the source of brake noise. Measurements of the position of the dynamic centre of pressure (CoP) support the theoretical predictions that a leading CoP induces brake noise. Design proposals are suggested that may be applied early in the design phase as a means to reduce the propensity of a brake to generate noise.
    • The large strain response of polypropylene in multiaxial stretching and stress relaxation

      Sweeney, John; Caton-Rose, Philip D.; Spencer, Paul E.; Pua, H.; O'Connor, C.P.J.; Martin, P.J.; Menary, G. (2013)
    • The pattern of surface waves in a shallow free surface flow

      Horoshenkov, Kirill V.; Nichols, Andrew; Tait, Simon J.; Maximov, G.A. (2013)
      This work presents new water surface elevation data including evidence of the spatial correlation of water surface waves generated in shallow water flows over a gravel bed without appreciable bed forms. Careful laboratory experiments have shown that these water surface waves are not well-known gravity or capillary waves but are caused by a different physical phenomenon. In the flow conditions studied, the shear present in shallow flows generates flow structures, which rise and impact on the water-air interface. It is shown that the spatial correlation function observed for these water surface waves can be approximated by the following analytical expression W(rho) = e(-rho 2/2 sigma w2)COS(2 pi L-0(-1)rho). The proposed approximation depends on the spatial correlation radius, sigma(w), characteristic spatial period, L-0, and spatial lag, . This approximation holds for all the hydraulic conditions examined in this study. It is shown that L-0 relates to the depth-averaged flow velocity and carries information on the shape of the vertical velocity profile and bed roughness. It is also shown that sigma(w) is related to the hydraulic roughness and the flow Reynolds number.
    • The relationship between 2D static features and 2D dynamic features used in gait recognition

      Alawar, Hamad M.M.A.; Ugail, Hassan; Kamala, Mumtaz A.; Connah, David (2013)
    • The role of spectrum manager in IEEE 802.22 standard

      Afzal, Humaira; Mufti, Muhammad R.; Nadeem, M.; Awan, Irfan U.; Khan, U.S. (2014)
      The IEEE 802.22 is the first worldwide standard for wireless regional area network (WRAN) based on cognitive radio techniques. It provides access to use unused TV band without causing any harmful interference to the incumbents. This paper aims to elaborate the significance of the Spectrum Manager (SM) in WRAN Base Station (BS). It is responsible to maintain spectrum availability information of the cell. Using incumbent database, geolocation and spectrum sensing results, the SM defines the status of the channels with respect to incumbent detection. On the basis of channel status, the SM classifies the channel into different categories. A pseudocode has been proposed for the SM to perform channel decision process in two steps. Spectrum etiquette procedure is activated due to incumbent detection, neighboring WRAN cell detection/update, operating channel switching request and contention request obtained from neighboring WRAN cells. An example is given to demonstrate this procedure in a WRAN cells. Spectrum handoff mechanisms is initiated through the SM either when primary user is detected on the licensed channel or when the specified transmission time is terminated as discussed in the IEEE 802.22 standard. Other responsibilities of the SM are to impose IEEE 802.22 policies within the cell to ensure incumbent protection and maintain QoS in WRAN system. The policies are concerned with events and their corresponding actions. The SM also controls the sensing behavior of the Spectrum Sensing Automation (SSA), where SSA is an entity that must be present in all IEEE 802.22 devices which performs spectrum sensing through spectrum sensing function (SSF) after receiving request from SM.
    • The sustainability of noise barriers for EU project QUIESST: a case study

      Oltean-Dumbrava, Crina; Watts, Gregory R.; Miah, Abdul H.S. (2013)
    • The use of kurtosis de-noising for EEG analysis of patients suffering from Alzheimer's disease

      Wang, G.; Shepherd, Simon J.; Beggs, Clive B.; Rao, N.; Zhang, Y. (2015)
      The use of electroencephalograms (EEGs) to diagnose and analyses Alzheimer's disease (AD) has received much attention in recent years. The sample entropy (SE) has been widely applied to the diagnosis of AD. In our study, nine EEGs from 21 scalp electrodes in 3 AD patients and 9 EEGs from 3 age-matched controls are recorded. The calculations show that the kurtoses of the AD patients' EEG are positive and much higher than that of the controls. This finding encourages us to introduce a kurtosis-based de-noising method. The 21-electrode EEG is first decomposed using independent component analysis (ICA), and second sort them using their kurtoses in ascending order. Finally, the subspace of EEG signal using back projection of only the last five components is reconstructed. SE will be calculated after the above de-noising preprocess. The classifications show that this method can significantly improve the accuracy of SE-based diagnosis. The kurtosis analysis of EEG may contribute to increasing the understanding of brain dysfunction in AD in a statistical way.
    • Theoretical and conceptual issues in leadership and complex military operations

      Adeka, Muhammad I.; Shepherd, Simon J.; Abd-Alhameed, Raed A. (2016)
      This paper discusses theoretical and conceptual issues in leadership and how these apply to complex military operations in this global age. It identifies the reason for and the point at which the need for leadership arose among the early humans. It suggests the need for every human activity to be assessed within the context of its relative existence, based on the employment of accepted standards. Thereafter, the subject matter was treated under four main sections; namely, the Elements of Power, Leadership and its Sanctity, Concept of Military Operations, and Analosynthesis. With improvements in technology and mastery over their environments, the homo habilis gained control over their means of subsistence and the basic necessities of life. Their quest for better security and stability, in order to facilitate progressive developments, led to the emergence of community life. This was the stage at which the need for leadership, among humans, became apparent. Lessons on Leadership and Influence dictate that Power and Influence, which is one’s art of getting others to follow one’s lead, are best understood in terms of the interactions among the Elements of Power. The paper identified five enabling factors of power and influence; namely, how power works, how influence works, the TOPS Formula, the influence skills and cultural differences. These would enhance his ability to positively communicate with the led for maximum effect. Defined as a process of influencing a group of individuals to achieve a common goal, leadership is seen as a key variable in the development of human society. Any leader that fails to imbibe some ethical leadership values and principles that would guide his leadership, he would hardly gain the confidence and loyalty of the led. These include respect for others; service to others; justice, fairness and equity for all and sundry; honesty; resourcefulness; and truthfulness/trustworthiness – all leading to the building of a strong, united, virile and prosperous community. It is believed that the crises bedevilling Nigeria today, particularly Northern Nigeria, can be largely attributed to the negation of ethical values/principles on the part of our leaders, both past and present. It is hoped that the Change which Nigerian electorates voted for on 28th March 2015 would make the needed difference. A military operation is a set of activities characterised by mutual belligerent actions; regardless of how the opposing elements are defined, equipped or disposed. Hence, military operations may not be limited to the conventional battlefield; new forms of battlefields and domains of warfare will continue to emerge for as long as human technology is progressive. Currently, a critical analysis yields the existence of five warfare domains; namely, Land, Sea, Air, Space (Strategic Defence Initiative or Star Wars) and Cyber Space. In view of the above, even the concept of military operation, in terms of the troops that execute warfare, must also be re-assessed in tune with the dictates of globalisation. Thus, as opposed to seeing soldiers as some illiterates, dressed in ragtag attire and engaging in a “woo-chebe!” warfare; the contrary should now be the case. Soldiering should be seen as an enterprise for people traversing the entire levels of education/training throughout the social strata of the society; comprising the illiterate and semi-illiterate local informants, highly educated troops, and all shades of professionals and technocrats up to the University Professors, globally. Concomitantly, there is need to also re-evaluate, by reconfiguring and expanding, the concept of the military element of national power into a more suitable gauge of national strength - the socio-military element of national power. That is, the military is no longer expected to function effectively independent of its wider society setting. In a nutshell, for one to succeed as a leader of officers and men in a military operation, one must first of all imbibe the general principles/values of ethical leadership expected of all categories of leaders, as enumerated above. In addition to these, one must then train to internalise those other attributes that would sustain one in leadership position as one confronts an uncertain death; namely, valour, bravery, courage, faithfulness and an existence of a balanced coordination between a healthy mind and a healthy body.
    • Theoretical and finite-element investigation of the mechanical response of spinodal structures

      Read, D.J.; Teixeira, P.I.; Duckett, R.A.; Sweeney, John; McLeish, T.C.B. (EDP Sciences, 2002)
      In recent years there have been major advances in our understanding of the mechanisms of phase separation in polymer and copolymer blends, to the extent that good control of phase-separated morphology is a real possibility. Many groups are studying the computational simulation of polymer phase separation. In the light of this, we are exploring methods which will give insight into the mechanical response of multiphase polymers. We present preliminary results from a process which allows the production of a two-dimensional finite-element mesh from the contouring of simulated composition data. We examine the stretching of two-phase structures obtained from a simulation of linear Cahn-Hilliard spinodal phase separation. In the simulations, we assume one phase to be hard, and the other soft, such that the shear modulus ratio ... is large (... ). We indicate the effect of varying composition on the material modulus and on the distribution of strains through the stretched material. We also examine in some detail the symmetric structures obtained at 50% composition, in which both phases are at a percolation threshold. Inspired by simulation results for the deformation of these structures, we construct a "scaling" theory, which reproduces the main features of the deformation. Of particular interest is the emergence of a lengthscale, below which the deformation is non-affine. This length is proportional to ... , and hence is still quite small for all reasonable values of this ratio. The same theory predicts that the effective composite modulus scales also as ..., which is supported by the simulations.
    • Theoretical approach of freeze seawater desalination on flake ice maker utilizing LNG cold energy

      Cao, W.; Beggs, Clive B.; Mujtaba, Iqbal M. (2015-01-01)
      In this work, a novel concept in freeze desalination (FD) was introduced. Nowadays the total liquefied natural gas (LNG) production capacity has reached 290 Megatons per year. Its enormous cold energy released from re-gasification can be used in the freeze desalination process to minimize the overall energy consumption. A process of FD on flake ice maker utilizing LNG cold energy was designed and simulated by HYSYS software. An ice bucket on flake ice maker was chosen as seawater crystallizer mainly due to its continuous ice making and removing ice without heat source. A dynamic model of the freezing section has been developed and simulated through gPROMS software. The results show that the consumption of 1 kg equivalent LNG cold energy can obtain about 2 kg of ice melt water. In addition, it is shown that the power consumption of this LNG/FD hybrid process is negligible.
    • Theoretical Model to Determine the Blocking Probability for SDMA Systems.

      Galvan-Tejada, Giselle M.; Gardiner, John G. (2001)
      Antenna array technology has attracted the attention of the research community as a means to increase system capacity and improve the signal reception. Space division multiple access (SDMA) is a multi-access scheme based on the use of antenna arrays to separate users by exploiting their positions in space. Several works have been carried out to examine the improvement in the system capacity provided by SDMA. A theoretical model to determine the blocking probability for SDMA is derived. A closed-form linear system of equations is obtained whose numerical solution gives the blocking probability. The formulation is employed to assess the capacity gain improvement of a single-cell system under specific conditions. It is found from the results that SDMA is not efficient for low traffic loads, whereas it is so for high traffic.
    • Thermal Analysis of Convective-Radiative Fin with Temperature-Dependent Thermal Conductivity Using Chebychev Spectral Collocation Method

      Oguntala, George A.; Abd-Alhameed, Raed A. (2018-03-15)
      In this paper, the Chebychev spectral collocation method is applied for the thermal analysis of convective-radiative straight fins with the temperature-dependent thermal conductivity. The developed heat transfer model was used to analyse the thermal performance, establish the optimum thermal design parameters, and also, investigate the effects of thermo-geometric parameters and thermal conductivity (nonlinear) parameters on the thermal performance of the fin. The results of this study reveal that the rate of heat transfer from the fin increases as the convective, radioactive, and magnetic parameters increase. This study establishes good agreement between the obtained results using Chebychev spectral collocation method and the results obtained using Runge-Kutta method along with shooting, homotopy perturbation, and adomian decomposition methods.
    • Thermal and hydraulic properties of sandy soils during drying and wetting cycles

      Ali, Alexis; Mohamed, Mostafa H.A.; Aal, M.; Schellart, A.; Tait, Simon J. (2014)
      There is an increasing interest in the use of Ground Source Heat Pumps (GSHPs) as a source of renewable energy in temperate countries. GSHPs coupled with buried heat collectors can harness the thermal energy from near-surface soils to provide the heating required for domestic properties. The performance of a GSHP system depends greatly on the thermal conductivity of the surrounding soils. Near-surface soils undergo cycles of drying and wetting due to, for example, the infiltration of rain water and/or fluctuations of the ground water table. Several parameters - including the properties of soil, suction head and saturation history - affect the thermal properties as well as the retention and flow of water. This paper presents results from a comprehensive laboratory investigation on sand samples with markedly different grain size distribution. Simultaneous measurements of thermal and hydraulic properties of the sands were taken under incremental increase/decrease in the suction head values to simulate cycles of drying and wetting. The results clearly suggest that the thermal conductivity is better expressed as a function of the matric suction head so as to reflect the saturation history. There has been almost five-fold increase in the measured value of thermal conductivity when the soil was wetted to a residual degree of saturation from being dry.
    • Thermal contact resistance in micromoulding.

      Gonzalez Castro, Gabriela; Babenko, Maksims; Bigot, S.; Sweeney, John; Ugail, Hassan; Whiteside, Benjamin R. (2011-12)
      This work outlines a novel approach for determining thermal contact resistance (TCR) in micromoulding. The proposed technique aims to produce TCR predictions with known confidence values and combines experimental evidence (temperature fields and contact angle measurements) with various mathematical modelling procedures (parametric representation of surfaces, finite element analysis and stochastic processes). Here, emphasis is made on the mathematical aspects of the project. In particular, we focus on the description of the parametric surface representation technique based on the use of partial differential equations, known as the PDE method, which will be responsible for characterizing and compressing micro features in either moulds or surface tools.
    • Thermal optimisation of polymer extrusion using in-process monitoring techniques

      Vera-Sorroche, Javier; Kelly, Adrian L.; Brown, Elaine C.; Coates, Philip D.; Karnachi, N.; Harkin-Jones, E.; Li, K.; Deng, J. (2013)
      Polymer extrusion is an energy intensive process, which is often run at less than optimal conditions. The extrusion process consists of gradual melting of solid polymer by thermal conduction and viscous shearing between a rotating screw and a barrel; as such it is highly dependent upon the frictional, thermal and rheological properties of the polymer. Extruder screw geometry and extrusion variables should ideally be tailored to suit the properties of individual polymers, but in practice this is rarely achieved due to the lack of understanding of the process. Here, in-process monitoring techniques have been used to characterise the thermal dynamics of the extrusion process. Novel thermocouple grid sensors have been used to measure melt temperature fields within flowing polymer melts at the entrance to an extruder die in conjunction with infra-red thermometers and real-time quantification of energy consumption. A commercial grade of polyethylene has been examined using three extruder screw geometries at different extrusion operating conditions to understand the process efficiency. Extruder screw geometry, screw rotation speed and set temperature were found to have a significant effect on the thermal homogeneity of the melt and process energy consumed. (C) 2012 Elsevier Ltd. All rights reserved.
    • Thermal prediction of convective-radiative porous fin heatsink of functionally graded material using adomian decomposition method

      Oguntala, George A.; Sobamowo, G.; Ahmed, Y.; Abd-Alhameed, Raed A. (2019-03)
      In recent times, the subject of effective cooling have become an interesting research topic for electronic and mechanical engineers due to the increased miniaturization trend in modern electronic systems. However, fins are useful for cooling various low and high power electronic systems. For improved thermal management of electronic systems, porous fins of functionally graded materials (FGM) have been identified as a viable candidate to enhance cooling. The present study presents an analysis of a convective–radiative porous fin of FGM. For theoretical investigations, the thermal property of the functionally graded material is assumed to follow linear and power-law functions. In this study, we investigated the effects of inhomogeneity index of FGM, convective and radiative variables on the thermal performance of the porous heatsink. The results of the present study show that an increase in the inhomogeneity index of FGM, convective and radiative parameter improves fin efficiency. Moreover, the rate of heat transfer in longitudinal FGM fin increases as b increases. The temperature prediction using the Adomian decomposition method is in excellent agreement with other analytical and method.